The present invention relates generally to tools used to make one or more dados in a workpiece. More specifically, the present invention relates to woodworking tools used to align a workpiece relative to a cutting element to cut one or more dados.
Shelving for cabinets, book shelves, drawers and the like often include brackets to secure horizontal members or cross members to vertical members. However, a common method of fabricating this type of furniture is by cutting dados in the vertical member, whereby the dados have a width dimension corresponding to a thickness dimension of the cross members. Opposite ends or edges of the cross members are inserted into the dados. Glue and/or fasteners may be provided to strengthen the interface between the cross members and vertical members.
Dados are typically cut on a table saw with a dado saw blade set or dados may be cut using a router with a pre-determined cutting diameter router bit secured at a desired bit height. A dado saw blade set consists of multiple saw blades that may have the same or differing thickness stacked together so the blade sets have a thickness corresponding to a thickness of the shelves. A stack of dado shims are inserted between consecutively aligned saw blades to more precisely match the width of the dado saw blade set to the thickness of the cross members. A disadvantage of using a dada saw blade set is that this thickness matching step may require several trial and error test cuts.
Moreover, the blades of a dado saw blade set usually have a smaller diameter relative those saw blades that are typically used for making cuts, or removing material, thereby requiring a different saw blade insert. In addition, certain table saws may require different safety equipment to be installed in order to use dado saw blades having the smaller diameter.
The stacked dado saw blade set usually removes two to eight times more material than a typical saw blade, requiring a more powerful motor to drive the dado saw blade set and a well-maintained table saw to effectively and safely cut a dado with stacked dado saw blades. This often adds a significant amount of expense and a significant time consuming setup. To that end, it is recommended, for safety reasons, to not use a dado blade set on an under-powered table saw.
Each saw blade on the market has a blade body thickness and an offset dimension between the blade body and the width of carbide tips that are unique to a respective blade make and model. However, these dimensions may vary even for the same model made by the same manufacturer. The differing dimension between two blades can be as small as a few thousands of an inch to about sixty thousands of an inch. In addition, every saw blade gets dull after a period of time and needs to be sharpened. Every sharpening changes the offset dimension, because the carbide tips will be grounded narrowing the carbide tip, which alters the offset dimension. Each of these variable dimensions makes the setup of a dado saw blade difficult to precisely match the width of a dado cut or cross member without trial and error test cuts.
Many table saw operators use plywood router bits instead of a dado saw blade set; however, plywood router bits create a different problem. There are router bits made specifically for plywood shelving and are manufactured to specific diameters. However, the set thickness on sheets of plywood in today's market may vary from sheet to sheet and these varying thickness do not match the set diameters of the plywood router bits. Because of the fixed cutting diameter of the plywood router bits, almost every cut is either oversized or undersized. This creates an undesirable fit and affects the strength of the shelving unit.